1. Field of the Invention.
The invention is related to a class of devices known as thermal viewers. There are many devices that fall in this category including a variety of image orthicons having retinas responsive to very long wavelengths of infrared light, e.g. greater than one micron. Most of the current devices, however, utilize small individual detecting elements or diodes over which the infrared image is scanned. A very popular device at present uses a row of diodes equal in length to one dimension of the infrared image. The output of these detectors produces a video type signal that can be processed in various ways to provide a visible image. One way is to convert the information to a normal TV format and display the image on a commerical TV receiver. Another way is to provide a receiver with scan signals to match the mirror scanned image in the thermal viewer. One simple technique widely used is to provide a light emitting diode coupled to each detector and to scan the visible image thus produced using the silvered back of the same mirror that scans the infrared image. The image obtained though usually recognizable is quite different from a normal image of the target or scene being observed. This is due mainly to the fact that the image is emitted by rather than reflected from the target and is proportional to the temperature of its various areas. It is also partly due to the constrainst of the viewer itself involving mainly the size of the detectors, their total response and the rate at which they respond. The information available in these images, although much less than that generally found in reflected light images, is none-the-less valuable because the information is nearly one hundred percent dependent on the character of the target and is very difficult to camouflage. To utilize this information, however, there must be a course of training to provide the observer with comprehensive background experience in its interpretation.
2. Description of the Prior Art.
The images produced by thermal viewers have been recorded in the past with black and white as well as color photography. Since the viewers are still relatively expensive and scarce, the use of photographic images for trainee users is very compelling. The latter also aleviates the problem of providing real targets such as tanks, planes and even large ground installations. Thus far, however, the photographic approach has been unsatisfying. Even color photography lacks the realistic, live environment essential to proper training.